A variety of tools have been proposed or used to detect flaws in integrated circuits. The detection and correction process, often referred to as “debugging,” includes failure analysis and fault isolation (FAFI). The design of an integrated circuit can often be tested by simulating or emulating the operation of the circuit using computer programs and separate logic components.
An integrated circuit may also be tested by providing a variety of input signals to the input pins of the integrated circuit and observing the output signals provided by the integrated circuit at its output pins in response to the input signals. A circuit having some types of defects may when operated, provide an output signal at an output pin which differs significantly from that provided by an integrated circuit having the same circuit design but known to lack defects. Hence, the output signals at the output pins of an integrated circuit being tested may be noted while the circuit is being operated and the resulting output signals compared to known outputs of known flawed and unflawed circuits to detect whether a flaw exists in the integrated circuit being tested.
In addition to noting the output signals provided at the output pins of an integrated circuit being tested, it is known that a defect in an integrated circuit may provide electromagnetic emissions which differ from the electromagnetic emissions of the same circuit portion in an integrated circuit which is known to lack those defects. For example, FIG. 1 is a schematic diagram of an InfraRed Emission Microscope (IREM) 10 which can detect local switching and leakage currents through the detection of emitted photons. The IREM 10 includes an optical system 12 which includes a primary lens optics 14 which focuses on a particular portion of an integrated circuit device 16 under test. The photon emissions of the integrated circuit portion being operated are collected by the primary lens optics 14 and focused by a secondary lens 18a of a carousel 20 of second lenses 18a, 18b, 18c, onto a sensor array 22. The output signals of the sensor array 22 may be collected by a processor or logic circuit 24 which can compare the images of various portions of the device 16 being tested to corresponding images of known flawed and unflawed circuits to detect whether a flaw exists in the integrated circuit device 16 being tested.
There are additional types of debugging tools. For example, it has been noted that circuit operation may be affected by illuminating a portion of an integrated circuit with a laser beam. Moreover, a circuit having some types of defects being illuminated by a laser may provide an output signal at an output pin which differs significantly from that provided by an integrated circuit having the same circuit design but known to lack defects. Hence, the output signals at the output pins of an integrated circuit may be noted while the circuit is being operated and illuminated by a laser and the resulting outputs at the circuit output pins compared to known output signals at the output pins of flawed and unflawed circuits to detect whether a flaw exists in the integrated circuit being tested.
FIG. 2 is a schematic diagram of a Laser Assisted Device Alteration (LADA) debugging tool 28 which includes a laser source 30 and a scanning optical system 32 which can focus the laser beam 34 using an objective lens 36, on a particular portion of the integrated circuit device 38 being tested. A scanning mirror 40 of the optically system 32 can direct the laser beam 34 to illuminate the desired locations of the device 38. The output signals at the output pins of the device 38 may be collected by a processor or logic circuit 42 while the integrated circuit is being operated and illuminated by the laser 30. The logic circuit 42 can compare the resulting outputs at the circuit output pins of the device 38 to known output signals at the output pins of flawed and unflawed circuits to detect whether a flaw exists in the integrated circuit device 38 being tested. A mirror 50 can split the laser beam 34 to provide a sample beam 34a which is directed by other mirrors such as mirror 52 to a sensor 54, the output of which may be used to regulate the power of the laser 30.